Voltase hobby

Buying a gift for someone special or a loved one can sometimes be difficult or expensive. The flashing heart is the answer. It is easy to build and even the inexperienced hobbyist should be able to build it. The estimated cost for the circuit is $25 if all the parts are purchased new. With The Flashing Heart, you can get your message across in bright lights.

The collectors of Q2 and Q3 are connected to R4 and R5 respectively, which are connected to the cathodes of the Yellow LEDs. Pin 13 is the oscillator output and is connected to R8, which is connected to the base of Q1. The collector of Q1 is connected to R3, which is connected to the cathodes of the Red LEDs. The emitters of the three transistors are connected to ground. The Green LEDs are connected to R1 and R2, which are connected to +12VDC. Resistors R1-R8 are current limiting resistors and the correct wattage for these resistors should be used to prevent excessive heat. The resistive values may be changed to vary the brightness of the LEDs. The circuit is powered by PS1, a wall transformer, which is connected to a filter capacitor C1. It must be between 10 to 15 VDC and at least 500mA.

Circuit Description The Circuit Diagram is shown in Figure 1. It consists of a 4047 low-power monostable/astable multivibrator, IC1, used in the astable mode to provide the timing pulses to control the flash rate of the LEDs. To accomplish the astable mode, pins 4, 5, 6, and 14 are connected to +12VDC and pins 7, 8, 9, and 12 are connected to ground. Pins 1 and 3 are connected to C2 and pins 2 and 3 are connected to potentiometer R9. A fixed value resistor can be used in place of the potentiometer R9, if the flash rate does not need to be adjusted. These three pins make up the R-C timing circuit. The output pulses from the 4047 are taken from pins 10, 11, and 13. Pin 10 is the Q output and pin 11 is the Q-not output. These two pins are onnected to R6 and R7 respectively.

The following diagram is a very easy and efficient receiver for actuating garage doors, starter motors, alarms, warning systems and numerous some other possibilities.



The SCR, that has a extremely low trigger present of 30 uA is common -- it requires an input electric power of just 30 uW to switch on the relay. A high Q tuned antenna schema assures rejection of spurious signals. A whip or wire antenna is adequate as much as 100 feet from a low power transistor transmitter. A momentary-off switch resets the schema.

The schema specifies a whip or wire antenna which just indicates a solid piece of wire 6-12 inches long (15-30cm). The antenna coil is experimental, however you can start with ten to 12 turns of #22 (0.7mm) magnet wire, and 5/16" (8mm) coil diameter. Antenna wire is soldered at 1/2 turn of the coil and the gate of the BRY35 is soldered about halfway the coil. This schema will transmit as much as 100-feet with the above specs @ 30uA.

The relay coil is specifys as much as 200 ohm but thats just the one I had in stock. Any low-ohm relay, even at 9V or so, ought to accomplish the task. And one remaining note, do not be expecting too a lot from this schema. The "Very Easy R/C Circuit" is simply that; Easy!

The BRY35 is really an classic semiconductor produced by Philips. A great replacement would be the EC103D1, also produced by Philips (see pin-out picture for this device). NTE Semiconductors gives an alternative of NTE5405, but I have not attempted it. I think, a NTE5400 (30V) or NTE5401 (60V) will function just also. The NTE5405 is a bit overkill at 400V.